Hi,
I have used Easybus from Luton on two occasions without any problems. They use modern coaches and the pick up is located just outside the terminal. The drive into London is dependent on traffic of course but it wasn't too bad either time for me. Unless you're in a mad hurry it shouldn't be an issue.
I would consider using them to Stansted in the future as they are quite a bit cheaper than the train. BTW it is also cheaper to book in advance online.